I'll have a dig around and see if I have anything on those 'superbombers'. I assume you've already read Tony Buttler's British Secret Projects: vol 3, I know that it will be revamped and republished as two volumes, fighters and bombers within the next year or so. Hopefully it might have more information on those 'Ideal Bombers' and later-war super-heavy types if anything has surfaced from the archives. Of course its possible that little work beyond those rough sketches was ever done.